import {Curve, Vector3, Vector4} from '../../build/three.module.js'
import {NURBSUtils} from '../curves/NURBSUtils.js'

/**
 * NURBS curve object
 *
 * Derives from Curve, overriding getPoint and getTangent.
 *
 * Implementation is based on (x, y [, z=0 [, w=1]]) control points with w=weight.
 *
 **/

var NURBSCurve = function (degree, knots /* array of reals */, controlPoints /* array of Vector(2|3|4) */, startKnot /* index in knots */, endKnot /* index in knots */) {
  Curve.call(this)

  this.degree = degree
  this.knots = knots
  this.controlPoints = []
  // Used by periodic NURBS to remove hidden spans
  this.startKnot = startKnot || 0
  this.endKnot = endKnot || this.knots.length - 1
  for (var i = 0; i < controlPoints.length; ++i) {
    // ensure Vector4 for control points
    var point = controlPoints[i]
    this.controlPoints[i] = new Vector4(point.x, point.y, point.z, point.w)
  }
}

NURBSCurve.prototype = Object.create(Curve.prototype)
NURBSCurve.prototype.constructor = NURBSCurve

NURBSCurve.prototype.getPoint = function (t, optionalTarget) {
  var point = optionalTarget || new Vector3()

  var u = this.knots[this.startKnot] + t * (this.knots[this.endKnot] - this.knots[this.startKnot]) // linear mapping t->u

  // following results in (wx, wy, wz, w) homogeneous point
  var hpoint = NURBSUtils.calcBSplinePoint(this.degree, this.knots, this.controlPoints, u)

  if (hpoint.w != 1.0) {
    // project to 3D space: (wx, wy, wz, w) -> (x, y, z, 1)
    hpoint.divideScalar(hpoint.w)
  }

  return point.set(hpoint.x, hpoint.y, hpoint.z)
}

NURBSCurve.prototype.getTangent = function (t, optionalTarget) {
  var tangent = optionalTarget || new Vector3()

  var u = this.knots[0] + t * (this.knots[this.knots.length - 1] - this.knots[0])
  var ders = NURBSUtils.calcNURBSDerivatives(this.degree, this.knots, this.controlPoints, u, 1)
  tangent.copy(ders[1]).normalize()

  return tangent
}

export {NURBSCurve}
